xds: Non-SOTW resources need onError() callbacks, too (grpc#12122)

SOTW is unique in that it can become absent after being found. But if we
NACK when initially loading the resource, we don't want to delay, depend
on the resource timeout, and then give a poor error.

This was noticed while adding the EDS restriction that address is not a
hostname and some tests started hanging instead of failing quickly.

Author: ejona86

xds/src/main/java/io/grpc/xds/client/XdsClientImpl.java

@@ -592,12 +592,6 @@ private <T extends ResourceUpdate> void handleResourceUpdate(
         subscriber.onRejected(args.versionInfo, updateTime, errorDetail);
       }
 
-      // Nothing else to do for incremental ADS resources.
-      if (!xdsResourceType.isFullStateOfTheWorld()) {
-        continue;
-      }
-
-      // Handle State of the World ADS: invalid resources.
       if (invalidResources.contains(resourceName)) {
         // The resource is missing. Reuse the cached resource if possible.
         if (subscriber.data == null) {
@@ -607,6 +601,11 @@ private <T extends ResourceUpdate> void handleResourceUpdate(
         continue;
       }
 
+      // Nothing else to do for incremental ADS resources.
+      if (!xdsResourceType.isFullStateOfTheWorld()) {
+        continue;
+      }
+
       // For State of the World services, notify watchers when their watched resource is missing
       // from the ADS update. Note that we can only do this if the resource update is coming from
       // the same xDS server that the ResourceSubscriber is subscribed to.

xds/src/test/java/io/grpc/xds/GrpcXdsClientImplTestBase.java

@@ -3270,6 +3270,8 @@ public void edsDuplicateLocalityInTheSamePriority() {
         + "locality:Locality{region=region2, zone=zone2, subZone=subzone2} for priority:1";
     call.verifyRequestNack(EDS, EDS_RESOURCE, "", "0001", NODE, ImmutableList.of(
         errorMsg));
+    verify(edsResourceWatcher).onError(errorCaptor.capture());
+    assertThat(errorCaptor.getValue().getDescription()).contains(errorMsg);
   }
 
   @Test